Make invalid states hard or impossible to represent and parse external primitives into meaningful internal types at the edge. Use at data modeling, API design, or external data ingestion points.
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---
name: principle-type-system-discipline
description: Make invalid states hard or impossible to represent and parse external primitives into meaningful internal types at the edge. Use at data modeling, API design, or external data ingestion points.
---
# Type System Discipline
## Trigger
At data modeling, API design, or external data ingestion points.
## Rule
Make invalid states hard or impossible to represent and parse external primitives into meaningful internal types at the edge.
## Application
1. Name the concrete decision this principle changes.
2. Apply the rule to that decision, not as a decorative citation.
3. Prefer evidence from the current repository/runtime over generic preference.
4. If the principle conflicts with an explicit user constraint, keep the constraint and state the tradeoff.
